1. Field of Invention
The present invention relates generally to golf clubs and, more particularly, to golf club shafts.
2. Description of the Related Art
Over the years, many substitutes have been introduced for the hard wood shafts originally used in golf club drivers and irons. Early substitute materials included stainless steel and aluminum. More recently, carbon fiber reinforced resin shafts have become popular. Fiber reinforced resin shafts are typically hollow and consist of a shaft wall formed around a tapered mandrel. The mandrel typically consists of three mandrel sections. The first mandrel section forms the tip section of the shaft, the second mandrel section forms the main body section, and the third mandrel section forms the grip section. Shafts formed in this manner typically have a constant taper from the tip/main body intersection to the main body/grip intersection. Additionally, a grip is often placed over the grip section to facilitate the golfer's grasp of the club.
As shown in FIG. 1A, the grip section of a conventional shaft is often substantially cylindrical over its entire length. Here, the grip (shown in dotted lines) is tapered in an attempt to make the grip portion of the golf club, i.e. the portion which consists of the grip and the grip section of the shaft, conform to the shape of the golfer's hands. Referring to FIG. 1B, other conventional golf club shafts, often referred to as "large butt" shafts, include a grip section which tapers from one end to the other. Here, the thickness of the grip (shown in dotted lines) is substantially uniform over its entire length. As such, from the standpoint of the golfer's hands, the respective grip portions of the clubs shown in FIGS. 1A and 1B are essentially the same, i.e. there is a straight taper from one end of the grip portion to the other. The slope of the straight taper is typically such that the outer diameter of the grip portion decreases at a rate of 0.0285 inch/inch of shaft length.
The inventor herein has determined that there are a number of disadvantages associated with the conventional golf club shafts shown in FIGS. 1A and 1B. For example, the straight taper does not conform well to the contour of the golfer's hands. This is especially true with respect to the bottom hand, which is the right hand for right-handed golfers and the left hand for left-handed golfers. Additionally, there are many instances where a golfer will want to "choke up" on a club, i.e. move his or her hands to a lower position on the shaft, to decrease the distance the ball will travel. With a conventional club, this will change the golfer's top hand grip on the club, as well as the more important bottom hand and bottom thumb grip on the club, because the outer diameter (OD) of the grip portion of the club decreases from one end to the other.
Turning to FIG. 1C, another type of conventional shaft includes a main body section with a relatively large OD, a conventionally sized grip section and a short connecting section therebetween. Such shafts are often referred to as "wide body" shafts. Such a shaft is disclosed in U.S. Pat. No. 5,316,299 to Feche et al. The primary benefit of a wide body shaft is that, for a given shaft wall thickness, the wide body shaft will be stiffer than other conventional shafts. The stiffest portion of certain wide body shafts is the portion of the main body section which abuts the connecting section because this is where the OD of the main body section is the greatest. The inventor herein has determined that this can be undesirable for some golfers.